1. Technical Field
The present invention relates to compression fittings and more particularly to a compression fitting for mounting a sensor such as a thermoelectric or fluid mechanical sensor to an apparatus such as a gas turbine engine.
2. Background Information
Apparatus such as gas turbine engines which power aircraft and industrial equipment are typically instrumented for monitoring and controlling the engine's operation. For example, modern gas turbine engines are typically provided with a plurality of sensors such as thermocouples or other thermoelectric sensors which measure operating temperatures at various locations within an engine, pressure sensors which measure the pressure of working fluid at various locations within the engine and accelerometers which measure the vibration of mechanical components within the engine. Sensors such as the above noted thermocouples, pressure sensors and accelerometers usually include leads which transmit a signal indicative of the operating condition being measured to signal processing apparatus which may display the signal in a readable form to an operator of the engine or control the operation of the engine in response to the signal. In the case of electric sensors such as thermocouples and accelerometers, such leads are typically thin electrical conductors such as wires. In the case of fluid-mechanical sensors such as pressure sensors and the like, such leads are typically thin tubes which extend from the sensor to the signal processing apparatus such as the display apparatus or engine controller noted above. Sensor leads such as the above noted electrical and fluid mechanical wires and tubes are typically egress the engine through a sealed fitting which provides a pathway for the extension of the sensor leads to the signal processing apparatus. It will be appreciated that such sensor fittings must include a seal for preventing leakage of working fluid within the engine through the fitting to the engine's surroundings. Known sensor fittings include a body or housing through which the leads extend and a mechanical means for compressing the seal against the leads and the interior of the housing. Such mechanical seal compression means often take the form of a rotationally driven piston or follower through which the leads extend, interiorally of the fitting body. To prevent twisting or torque shearing of the leads extending through the follower, the follower must axially translate within the fitting body without rotation. Thus, it has been the practice to provide such sensor fittings with a small anti-rotation pin which engages the follower and fitting body to prevent rotation of the follower as it translates axially through the fitting body in compressing the fitting seal. It has been observed that in the assembly of the sensor fitting with the host engine, such small anti-rotation pins are often inadvertently omitted from the sensor fitting, thereby allowing the follower to rotate as it is moved axially to compress the seal material within the fitting, thus damaging or severing the leads extending through the follower. It has also been observed that such small anti rotation pins may separate from the fitting, to be ingested by the engine, thereby damaging critical rotational and stationary engine components such as blades, seals and the like.
Thus, there is a need for a fitting, by which provides a sealed egress for electrical or fluid mechanical sensor leads is from an apparatus such as a gas turbine engine, which prevents damage to the sensor leads extending through the fitting as seal material within the fitting is compressed against the sensor leads and the interior of the fitting's housing without the use of separate anti rotation parts such as the small anti-rotation pins noted above, which are often inadvertently omitted from of the fitting assembly or separated therefrom and ingested into the apparatus on which the fitting is used.